We will use cloned genomic fragments from the 1000-kb region of DNA amplified in PALA-resistant hamster cells to investigate the details of the amplification process, especially important structural features of the amplified unit, whether or not each cloned region is amplified to the same extent in independent events, whether or not transcriptional units other than the CAD gene are present within the amplified region and, if so, whether or not they are expressed in proportion to gene copy number. We also plan to look at cells early in the process of gene amplification in an attempt to characterize early structures and events in the process. We will also continue to characterize SV40 transcriptional complexes obtained late in infection, and to investigate the possibility that interferon blocks an uncoating event early in SV40 infections.